Telephone-exchange system.



A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

- APPLICATION FILED OCT. 2. I916. H. %%W @1 Patented Dec. 4, 1917;

4 SHEETSSHEET 1.

M ve m far: Albm f. Lynda/L A. E. LUNDELL. TELEPHONE sxcrmmez SYSTEM.

APPLICATION FILED OCT. 2. 1916.

Patented 10%., 4,1917.

4 SHEETS-SHEET 2- M a/eh fO/ A Ike/1 f. A MMm /V.

A. E. LUNDELLQ TELEPHONE EXCHANGE SYSTEM.

mmwmmw M van 1W.- A (ban f. Luna/6W.

A. E. LUNDELL'.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED OCT. 2, I916.

Patented Dec. 4:, 1917.

4 SHEETS-SHEET 4.

M van for: Awe/4 E. Lulma'ell.

TEN T ALBEN E. LUNIDELL, OF NEW YORK, N. '55., ASSIGNOR TO WESTERNELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N.

Y., A COBPQBATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern:

Be it known that I, Annniv E. LUNDELL, a citizen of the United States,residing at New York, in the county of Bronx and State of New York, haveinvented certain new and useful Improvements in Telephone- ExchangeSystems, of which the following is a full, clear, concise, and exactdescription. 7

The present invention relates to telephone exchange systems of the typewherein provision is made for observing from a central point thecharacter of service being rendered upon the telephone lines of theexchange. The invention is particularly adapted to service inmulti-oflice districts wherein the telephone lines at any of the officesmay be observed from a single observ ing station common to a number ofsuch offices.

In such systems the observing circuits or trunks extend from thedifferent central offices to the observing station. As soon as atelephone line is put into service it is brought into connection withthe observing circuit and from that time on signals are displayed beforethe observing operator to indicate the various operations upon the lineand the associated operators circuit. In order that the operator mayknow the particular line under observation, a signal corresponding tothat line is displayed before her.

In prior systems of this type, groups of relays and associated circuitshave been employed to display the signals corresponding to the telephonelines under observation. One object of the present invention is toperform this function by automatic traveling switches instead of relays.Another object of the invention is to provide novel circuits andapparatus for synchronously operating these automatic travelingswitches. With these objects in view, the invention consists in certainnovel arrangements of circuits and combinations of parts which will bemore fully understood upon refer ence to the following detaileddescription taken in connection with the accompanying drawing, while thescope of the invention will be more particularly set forth in theappended claims.

When the sheets of the drawing are arranged the order Figures 2, 3 a d4,

. Specification of Letters Patent.

Patented Dec. a, mi v. 1916. I SerialNo. 123,315. I

they illustrate a diagram of a telephone system constructed and arrangedin accordance with the present invention. In this diagram the observingcircuit extending from one central oflice to the observing station isrep-' resented. The central oflice circuits and apparatus are shown inFig. 1; the observing station is illustrated in Fig. 4; and the partsand apparatus of the intermediate portion of the observing circuit areshown in Figs. 2 and 3.

In the diagram two subscribers stations 10 and 11 are connected by lines12 and 13 to the central office, where they are provided with the usualjacks 14, 15, line relays 16, 17, line lamps 18, 19, and cut'olf relays20, 21. Line 12 is also shown provided with a message register 22. Atthe central office the operator is provided with a cord or link circuithaving plugs 23, 24, connected by tip strands 25, 26, and sleeve strands27 28, to the repeating coil windings 29 and 30. Supervisory relays 31,32 are provided in the tip strand, and in association with resistances33, 34, and 35, 36, control the supervisory lamps 37, 38. This cordcircuit is also provided with the usual ringing key 39 and otherequipment. A message register 40 is also associated with the cordcircuit. This register is common to the operators position and by meansof keys, such as 41, the register may be thrown into circuit withsubscribers lines. The cord circuit may be used to connect the linestogether directly or in conjunction with trunks, as is common inpractice. The subscribers lines and cord circuit illustrated are merelytypical of any exchange and in themselves form no part of the presentinvention.

The subscribers lines are provided with extension conductors 42 to 49,inclusive, by which the talking conductors are extended to the contactsof plugs 50 and 51, and the signaling conductors are extended to thecontacts of plugs 52 and 53. These plugs cooperate with jacks 54, 55,56, 57, respectively. The contacts of jacks 54 and 56 form the terminalsof talking conductors 58, 59, 60 and 61. Similarly the contacts of jacksand 57 form the terminals of signaling conductors 62, 63, 64 and 65.These various conductors form a connecting link between the subscriberslines and the conductors of the observing circuit pr trunk.

' subscrib'ers line 13 includes relays 72 to 77,

inclusive. The common listening conductors'78"and 79 of the observingcircuit are connected at one end in multiple to the contacts of relays67 and 73, and at the other end extend through the windings ofretardation coil 80 and repeating coil windings 81.

to'the contacts of relay 82. The repeating coil windings 83, whichcooperate with the windings 81, are in turn connected to listeningconductors 84 and 85 or the observing circuit, and these conductorsterminate in contacts o1"- a'listcning key 86 at the observing operatorsposition. The various con trol relays of Fig. 2 are connected with thecontrol relays of Fig. 3 by conductors 87 to 94, inclusive. The relaysof Fig. 3 which are associated more particularly with these conductors,are designated 95 to 100, inclusive. The relays of Fig. 3 associatedparticularly with the listening conductors 78, 7 9."are'designated 101to 105, inclusive.

In associationwitli the circuits and apparatus of Fig. 3, I employprimary automatic traveling switch 106. This switch is of the simplerotary type andlincludes brushes 107 and 108 which are adapted to travelover fixed contacts in response to the actuations of a motor magnet 109.The armature of the motor magnet is provided with a pawl 110 whichengages teeth on the ratchet wheel 111 to advance the brush arm 112 inthe usual way. A retaining pawl 113 holds the switch in its advancedposition whenever the holding magnet 114 is energized. A test relay 115is connected with the brush 108 and'serves to interrupt the advance ofthe switch in the usual way. Other relays employed more particularly inthe control 5 of the switch are designated 116 to 119, in-

elusive. The circuits of the control relays of Fig. 3 are connected byconductors 120, 121 and 122 to contacts of a position relay 123 locatedbefore the observing operator.

The parts and circuits illustrated in Figs. 2 and 3 are preferablylocated at the central ofiice in which the subscribers lines 12 and 13terminate. The conductors 84, 85, 120, 121' and 122 are trunk conductorsand connect the circuits of the central ofiice to the equipment at theobserving operators position.

The observing operator is provided with lamps which indicate theoperations per-- formed by the subscriber and operator in connectionwith any line under observation. The lamps 124 and 125 indicate thecharactor of the subscribers acts, and the lamps 126 and 127 show thecharacter of the operators acts. The lamps 124 and 126 are individual tothe observing trunk, while the lamps 125 and 127 are pilot lamps commonto the observing operators position. In addition to these, the observingoperator provided with a lamp 128 which indicates the operation of themessage register. A buzzer 129 is also provided for audibly indicatingthe same operation. Relays 130, 131 and 132 control the indicatinglamps, and relays 133 and 134 control the register lamp 128 and buzzer129. The observing operator is also provided with two keys 135 and 136by which the indications may be restricted. Normally the apparatus willindicate the operations in connection with the observed subscribersline, whether that line be a calling or called line. It the key 135) isthrown, then the indications will be limited to those which arise byreason ol tinline under observation being a calling line. Similarly ifkey 136 be thrown, then the indications will be limited to those whichoccur by reason of the line under observation being a called line. Relay137 comes into play in connection with the operation of these keys 135and 136. The observing operator is further provided with a series oflamps, of which those designated 138, 139, 140 are shown. Each of theselamps corresponds to a particular subscribers line which is availablefor observation. (onsequently, when a particular one of these lampslight, the observing operator knows exactly what line is underobservation. For

the purpose of bringing the proper lamp into circuit, I employ asecondary an tomatic traveling switch 141 which is similar inconstruction to the switch 106. It comprises brushes 142 and 143 whichtravel over fixed bank contacts in response to the actuations of motormagnet 144. The switch is held in its advanced positions by means of theholding magnet 145. The switches 106 and 141 operate in synchronism, thesecondary or follower switch 141 following the primary switch 106 stepby step. The circuits by which the control of these switches is broughtabout are controlled in part by the relays 146 to 152, inclusive. ingthe character of the operations by the various signals displayed beforeher, the observing operator is provided with a receiver 152 which may bebrought into circuit with the trunk conductors 8i and 85 by operatingthe listening key 86.

With this brief survey oi the various parts of the diagram, 1 mayproceed to a consideration of the operation of the svs tem and in sodoing the parts which have Besides observnot already been described willbe referred to in a way that will make their construction and operationapparent With the subscribers lines connected as shown, it may beassumed that the subscriber at substation 10 initiates a call. Uponremoving his receiver he will close a circuit from battery through hisline relay 16 and consequently light his line lamp 18, and at the sametime place a ground upon conductor 45, which will complete a circuitthrough conductor 63 and the lower winding of relay 68 to battery 153.The resulting operation of relay 68 will operate relays70 and 71 by acircuit which may be traced from battery 153 through closed contact 154,normal contact 155 ofrelay 69, thence through the-windings of relays 70and 71 in parallel, then through normal contact 156 of relay 71,conductor 90 and normal contact 157 of relay 98 to ground. Relay 71 isprovided with make-before-break contacts and, as soon as it isenergized, closes an alternative path through alternate contact 156,conductor 91, winding of relay 98 to ground, and breaks the circuitthrough conductor 90. As a result of the closing of this latter circuit,relay 98 is energized and complctes a circuit for locking magnet 99,which may be traced from battery 158 through closed key contact 159, thewindin of magnet 99 and alternate contact 157 0 relay 98 to ground. As aresult of the energization of relay 99, a locking circuit is closed frombattery 160 through closed contact 161, the winding of relay 99, andalternate contact 157 to ground. The energization of relay 70 alsocloses a circuit for relay 96 which may be traced from battery 162through the winding of relay 96, conductor 88, closed contact 163 ofrelay 70, conductors 63 and 45 to ground. The operation of relay 96closes a circuit for relay 131 which may be traced from battery 162,through closed con- 7 tact 164, normal contact 165 of relay 97 conductor122, normal contact 166 of relay 123, normal contact 167 of key 136, thewinding of relay 131, and normal contact 168 of relay 123 to ground. Theresulting energization of relay 131 closes a circuit for subscriberslamp 124 which may be traced from battery 169 through lamp 124 andclosed contact 17 0 to ground. The lighting of this lamp indicates tothe observer that a subscriber hasinitiated a call.

The energization of relay 96 also completes a circuit for relays 82 and103. This circuit may-be traced from ground through closed contact 171of relay 96 to the point 172 where it divides, one path going to battery173 through the winding of relay 82, and the other path going to battery174 through the winding of relay 103. The energization of relay 82closes the observers listening circuit from conductor 78 through titclosed contact 175 of relay 82, condenser 176 and alternate contact 177of relay 82 to conductor 79. As will appear later, the energi- Zation ofrelay 103 provides a maintaining circuit for relays 82 and 103 duringsubsequent operations.

As soon as the observing operator sees the subscribers individual lamp124 lighted, she will throw her listening key 86 and thereby connect hertelephone receiver 15L in circuit with conductors 84 and 85 throughclosed contacts 178 and 179 and condenser 180. The operation of thelistening key also closes contact 181 and thereby energizes positionrelay 123 by a circuit from battery 1.82 through the winding of relay123 and closed contact 181 to ground. The closing of listening keycontact 17 9 also closes a circuit for relays 117 and 146 which may betraced from battery 160 through closed contact 183, the winding of relay117, repeating coil winding 83, conductor 85, closed listening keycontact 179, closed off-normal switch contact 184, winding of relay 146,and alternate contact 168 of relay 123 to ground. The operation of relay117 closes a circuit for relay 118 which may be traced from battery 185through alternate contact 186 of relay 117 and the winding of relay 118to ground. The energization of relay 146 closes a circuit for relay 147which may be traced from battery 187 through the winding of relay 147and closed contact 188 of relay 146 to ground. The energization of theserelays 118 and 147 starts the automatic traveling switches 106 and 141.

In the operation of the automatic switches 106 and 141, the former,which is located at the outgoing end of the observing trunk, makes thefirst advance. When it has taken one step and is at rest, then theautomatic switch 141 at the incoming end of the trunk makes acorresponding step and comes to rest. Then the switch 106 againoperates, followed by a like operation of switch 141. Thus each switchmust perform its advance before the other can start, and consequently,exact synchronism between the two switches is obtained. The switch 106hunts out and seizes upon the line being observed, and the switch 141exactly following the operations of the switch 106, seizes upon a lampcorresponding to the observed line so as to indicate to the operator theparticular line under observation. The energization of relay 118 closesa circuit for control relay 119 and cut-0E relay 148 which may be tracedfrom battery 189 through closed contact 190 of relay 118, closed contact191 of relay 115, the winding of relay 119, conductor 120, closedcontact 192 of relay 123, the winding of cut-off relay 148, closedcontact 193 of relay 150, closed contact 194 of relay 151, and alternatecontact 168 of relay 123 to ground. The operation of cut-off rei lay 148opensthe normal ground connection from'brush 143 through contact 195 ofrelay '148 and normal contact 196 of relay 152. The 'energization ofrelay 119 closes the "circuit of motor magnet 109 from battery 195through closed contact 196 of relay 119t0 ground. To take care ofsparking, this contact is bridged by resistance 197 and a condenser 198in series. The energization of motor magnet 109 pulls down the pawl 110far enough to cause the brushes 107 and 108 to move out of engagementwith contacts 199 and 200 and into engagement with contacts 201 and 202.At the same time that relay 119 is energized, the holding magnet 114 isalso energized by a circuit from battery 203 through the winding ofmagnet 114, resistance 204 and alternate contact 205 of relay 118 toground. In consequence of the energization of relay 114 the holding pawl113 is moved into position to engage the'teeth'on the ratchet wheel 111and thereby hold the brushes in their advanced position. As soon asswitch brush 107 engages contact 201, a circuit is closed which willbring about an advance of the "switch 141. This circuit extends frombattery'185 through alternate contact 186, brush 107, contact 201,conductor 121, closed contact 206 of relay 123,'the winding of relay149, closed contact 207 of relay 147, and

alternatecontact 168 of relay 1 23 to ground.

The closing of this circuit results in energizing relay '149 and therebycloses the start ing circuit of switch 141, which may be traced frombattery 187 through closed contact 208 of relay 147, brush 142, switchcontact 209, the winding of relay 150, and alternate contact 210 ofrelay 149 to ground. The resulting energization of relay 150 closes acircuit for relay 152 which may be traced from battery 211 through thewinding of relay 152 and closed contact 212 of relay 150 to ground. Theresulting energization of relay 152 closes a circuit for the motormagnet 144 which extends from battery 213 through the winding of magnet144 and alternate contact 196 to ground. This energization of motormagnet 144 advances the brushes 142 and 143 from their normal positionin engagement with contacts 209 and 214 into engagement with contacts215 and 216. As soon as this position is reached the initial circuit forrelay146 over the listening conductor 85 is interrupted at theoff-normal contact 184, but the relay 146 is maintained energized byreason of the parallel path through closed contact 217 of relay 147.This advance of the switch 141 also opens the circuit of relay 150 atbrush 142. As a result, relay 150 becomes deenerg'ized, with aconsequent deenergization of relay 152 and motor magnet 144. It may bepointed out in connection with the operation of switch 141 that at thetime motor magnet 144is energized, the holding magnet 145 is alsoenergized to hold the switch in its advanced position by reason of acircuit extending from battery 218 through the winding of magnet 145,resistance 219 and closed contact 188 of relay 146 to ground. It willalso be noted that as soon as relay 150 is energized, the circuitthrough relay 119 of switch 106 is opened at contact 193 of relay 150,and consequently, the circuit of motor magnet 109 of switch 106 isinterrupted andthe advance of the switch beyond its first stepprevented. However, as soon as relay 150 becomes deenergized by reasonof brush 142 leaving contact 209, the circuit for relay 119 of switch106 is again established over conductor 120 and through the winding ofcutofl relay 148, normal contact 193 of relay 150, and normal contact194 of relay 151 to ground through alternate contact 168 of relay 123,as before. The reestablishinent of this circuit again energizes relay119 and causes motor magnet 109 to advance the wipers 107 and 108 ofswitch 106 out of engagement with contacts 201 and 202 and intoengagement with contacts 220 and 221. As a result of this advance,battery is not applied to conductor 121 through brush 107 as before,since conductor 121 is not connected to contact 220 as it was to contact201. Since it is not thus applied, relay 149 is deenergized with theresult that relay 151 becomes energized over a circuit extending frombattery 187 through closed contact 208, brush 142, contact 215, thewinding of relay 151, and alternate contact 210 of relay 149 to ground.This 'energization of relay 151 closes a circuit for relay 152 throughcontact 222 of relay 151, and the energization of relay 152 causes anadvance of the switch wipers into engagement with contacts 223 and 224.As soon as brush 142 disengages contact 223, the supply of battery torelay 151 is cut off and as relay 150 can not operate until relay 149has operated, the switch 141 remains in the third position. Both relays150 and 151 are again normal and the circuit through relay 119 at switch106 would be closed were it not for the action of the test relay 115.This relay is associated with the test wiper 108 of switch 106 and teststhe contacts 200, 202, 221, etc. When test Wiper 108 was in engagementwith contacts 200 and 202, no circuit was possible through the windingof relay 115 because contact 200 has no connection and contact 202 isconnected through conductor 225 to an open contact 226 of relay 77.However, as soon as test brush 108 engages contact 221 a circuit iscompleted which may be traced from battery 227 through the winding ofrelay 115, brush 108, contact 221, conductor 228, alternate contact 229of relay 71, conductor 91, and

tact 233 to ground.

mascara the winding o f relay 98 to ground. The closing of this circuitenergizes test relay 115 to interrupt the connection from battery 189and thereby prevent the closing of a circuit through control relay 119.In consequence of this operation of the test relay, the outgoingautomatic switch 106 is left in its third position with its brushes inengagement with contacts 220 and 221. In consequence of this stopping ofswitch 106, the automatic switch 141 is also left in its third positionwith its brushesin engagement with contacts 223 and 224. Since there isno circuit through relay 11.9, conductor 120 and relay 148, contact 195of relay 148 is closed, thereby providing a path for current for lamp139 which may be traced from battery 230 through lamp 139, switchcontact 224, brush 143, closed contact 195 of relay 148 and normalcontact 196 of relay 152 to ground. The lighting of lamp 139 indicatesto the observing operator that the telephone line 12 is the line underobservation.

As soon as the observing operator throws the listening key 86 inresponse to the lighting of the lamp 124 and thereby operates relay 123,as before pointed out, the circuit of relay 131 which controls lamp 124,is opened at normal contacts 166 and 168, and lamp 124 therebyextinguished. The shifting of these contacts to their alternatepositions connects conductor 122, which is supplied with current frombattery 162, into circuit with relay 132 through normal contact 231 ofrelay 134. "As a result, a circuit is closed for the subscribers pilotlamp 125 from battery 232 through lamp 125 and closed con- Thus theshifting of the listening key 86 throws the subscribers signal from thelamp 124 to lamp 125.

It will also be noted that the operation of relay 118 closes a lockingcircuit through relays and 71 in parallel. This circuit may be tracedfrom the live pole of battery 234' through closed contact 235 of relay118, conductor 94, closed contact 236 of relay 70, the windings ofrelays 7 0 and 71 in parallel,

' alternate contact 156 of relay 71, conductor 91, and the winding ofrelay 98. to ground. By this circuit the trunk is guarded against beingreleased before the observing operator restores her listening key tonormal after the subscribers operator has disconnected, and from anaccidental disconnection by an operator having control of the connectionbetween subscribers.

The operation of relay 117 at the outgoing end of the trunk circuitoperates relay 116 by closing a circuit which may be traced from battery185 through alternate contact 186 of relay 117 and the winding ofrelay116 to ground. In case relays 82 and 103 should release between thetimes that relay 96 is released and relay 105 is operated, then tacts252, 253

relay 116, by having conductor 237 con nected to ground through itsclosed contact 238, will enable these relays 82 and 103 to again operateand remain operated until the operator at the central ofiice takes downthe connection. However, the relay 116 has a different function when thesubscribers line is connected to as a called line.

When the subscribers operator at the exchange inserts plug 23 into jack14 in response to the display of the line lamp 18,a circuit is completedthrough cut-off relay 20 and relay 66 in parallel. This circuit extendsfrom batteries 239 and 240 through plug and jack local contacts toconductor 241, there dividing, one path going to ground through thewinding of relay 20 and the other path extending through conductors 44and 62 to ground through the winding of relay 66.. The resultingoperation of relay 66 closes a circuit which may be traced from battery242 through closed contact 243 of relay 66, alternate contact 244 ofrelay 70, conductor 87, and the winding of relay 95 to ground. Theenergization of relay 95 closes a circuit from battery 245 throughclosed contact 246 of relay 95, the winding of relay 105, conductor 247,repeating coil winding 83, trunk conductor 84, normal listening keycontact 248, and the winding of relay 130 to ground. The oppilot lamp127 by closing a circuit which may be traced from battery 249 throughlamp 127, alternate contact 250 of relay 123, and closed contact 251 ofrelay 130 to ground. The lighting of lamp 127 indicates to the observingoperator that the central oliice operator has responded to the call byinserting an answering plug into the jack of the calling line.

The operation of the line cut-off relay 2O interrupts the circuit of theline relay 16 and thereby extinguishes line lamp 18 in the usual way andremoves ground from conductor 45 by which relay 68 was initiallyenergized. In case relay 68 should momentarily release at this time, itwill be at once reenergized by reason of a circuit through its secondwinding which may be traced from battery 242 through closed contact 243,the winding of relay 67 and the second winding of relay 68 to ground.The operation of relay 67 in response to the closing of this circuitconnects the observing circuit conductors 78, 79, and 89 through closedconand 254 to conductors 58, 59, and 62, which are connected through theplugs and jacks to the extension conductors of the line underobservation. As a result of the operation of this relay 67, theobserving operator may listen to the conversation between the callingsubscriber and the 0perator at the central ofiice. I

By reason of the removal of the ground lji iiefrelay 16,"relay 96is'also deenergized.

Asfberore pbintedout, if relays "82. and 10,3

int

arei'eleased'fbefore relay105 is energized, then asj' soon, asthlatterrelay is energized they willagainbe operated by reason or theconnection. from the point 172 through closed contact 255 of relay'105,conductor 237 and closed contact 23801 relay 116' to ground. Irt'orderto prevent'any possible disturbance, in the circuit, the relays 82, and103;.T'arefprefeifably constructed so as to be sligh 'slow' release?,.Such disturbance in ght cause the central oliice operator'to suspect,that service on that line was being br e v, p "Kifterthe operator hasinserted the plug c s i ns jack '14, the; relay 1O2 will beoperht'edg'fromihe ope'r'ators cord,circu1t battery through thesubscribersinstrument in, parallel with 1 one; of the grounded anaiagsjitr the operators 001 a circuit repeatingjcoil. 9 The branch orthis circuit traced f'roriithe tip contact of the jack 1a throughconductors 4:2 53, closed contact 253 oiffre commer 7 8, closed contact17 ofrelay 82, the right-hand winding of relay 101 ,el osed contact 256of relay 101, the Win'ding of relay 102, normalcontact 257 of relay104c, and conductor 258 to ground.

which egitends through? relay 102 may be The contact259 of relay 102 isin multiple with contact 164 of relay 96 so that when thelatter rleasesiollovving the release of the'line relay 16, currentis suppliedfrom battery 1 260" through normal contact 165 V of rela'y 97toconductor 122 to maintain the subseribers' pilot signal 125-lighted aslong as subscriber at's'ubstation '10 has his receii er off. its heok.This relay 102, which is" 'jreferably aMorse relay, follows the movementof the subscribers sWitehhook softhatincase of a recall, the subscriberspilot lamp 125 will flashin a manner similar fto the flash"of'supervisory lamp 37 before the cen-tral otficeoperator.

nthe'condi ion at which we have arrived, both the subscribers andoperators pilot lanips 125 and 127 are lighted and the observerstelephone receiver 152 is bridged across the circiiit from thesubscribers stationi likewise the selecting'switches 106 and 1 11fhavestepped to a point corresponding to the number of the line underobservation. These automatic switches remain in their advanced positionsby reason or their holdinginagnets: which remain energized aslong as'the observing operators listening key 86 isjthrow n. t

the subscriberat the conclusion of conversation hangs up his receiver,the relay 102,is deenergized and batteryis thereby cut oftconductor122,with the resulting deenergization of relay and extinguishentiof ubs rier Pi a p 1 In case the circuit is equipped with message registers, thenthe operation of the message register key 11 by the operator at thecentral o'liice will close a circuit which may be traced from battery261 of reversed polarity through the winding of the magnet ot' theposition register 410, closed contact of key 4-1, plug and jack localcontacts, conductor 211, and thence dividing into three paths, one pathextending through cut-off relay 20 to ground, the second path throughthe windings of register 22 to ground, and the third from conductors4;1- and 62, alternate contact 251- of relay 67, conductor 89,throughthe winding of relay 97 to ground. The energization of relay 97connects a source or ringing current 262 into circuit, the circuitextending through. condenser 263, alterlrate contact 165 of relay 97,conductor 122, alternate contact166 of relay 123, the winding of relay133, and condenser 261 to ground; Theresulting energization of relay 133closes its contact 265 andthereby energizes relay 13-1 to cause thelighting of lamp 128. Relay 133. also causes the energization otthebuzzer magnet 129 to produce an audible signal. The circuit of lamp 128extends from battery 265 through lamp 128 and closed contact 266 ofrelay 13 1 to ground; Thebuzzer circuit'includes contact 267 a ndbattery268.

hen the] central ofiice operator takes down the connection bywithdrawingplug 23 n-Om' jack 14, relays 66, 67 and 68 aredeenergitechthe latter ,two by reason of the interruptionof. theircircuitat contact 2 13 of 'relay '6 6. The opening of this same contact243 also interrupts the circuit otrelay 95 and; thelatter in turn byopening its con tact 2&6 interrupts the circuit of relays 105 and 130.As a result of the deenergization of relay 130, the operators pilot lamp127 is extinguislred.

its soon as the observing operator notes that the operators pilot lamp127 is extinguished, she knows that the connection has beenptaken downand thereupon she restoresher listening hey 86 to its normal position,ihis results in restoring the several relays and-the automatic switchesto their normal position. The automatic switches are-restored to normalby a return spring (notshown) and during the return movemerit thedriving pawl is withdrawn from the teethofthe ratchet wheel by anysuitable mechanism. The withdrawal of the retaining pawl by reason ofthe deenergization otthe holding magnets 11 1 and 1 15, allows theswitch arm and the brushes connected thereto to return to normalposition. Thus the various parts of the system are restored to normaland are in condition for further service,

Heretoforev we have considered the case ofobservinga subscribers linewhere a call has originated on that line. We may now consider the casewhere the same subscribers line is observed but where it is connected toas a called line. As' soon as the central oflice operator, in responseto an order from a calling subscriber, inserts the plug 24 into jack 14:of the line 12 for the purpose of calling the subscriber on that line,the cut-off relay 20 and the relay 66 associated with the listeningconductors of the observing circuit operate as before, current beingsupplied in this instance from batteries 269 and 270, through the localplug and jack contacts, to conductor 2411, thence dividing, part goingto ground through relay 20 and part going to ground through conductors14-, 62, and the winding of relay 66. The operation of relay 66 closes acircuit from battery-242 through closed contact 243, closed contact 244,and the upper Winding of relay 68 to ground. The energization of relay68, as heretofore explained, brings about an energization of relays 70and 71, first over conductor 90 and then over conductor 91. As soon asrelay 70 operates, relay 67 which is normally short-circuited by normalcontact 2 11- of relay 70, is brought into circuit with the upperwinding of relay 68. Upon the resulting energization of relay 67, thelistening conductors 78 and 79 and the signaling conductor 89 areconnected to the conductors 58, 59 and 62, associated with the lineunder observation. The closing of the circuit of relays 70 and 71 overconductor 91 also results in energizing relay 98 and the associatedlocking relay 99, as before explained. As soon as relay 70 closescontact 2%, relay 95 operates over conductor 87 with a resultingoperation of relays 105 and 130, in the manner heretofore explained. Thelatter relay by closing its contact 251 lights the opera tors line lamp126 and thereby indicates to the observing operator that the central011186 operator has plugged into the line under observation.

As soon as the observing operator sees lamp 126 lighted, she throws herlistening key 86 and at once operates the position relay 123. At thesame time a circuit is completed for relays 117 and 146 over the listening conductor 85, as heretofore explained. As a result of theoperation of the position relay 123, lamp 126 is extinguished and theoperators pilot lamp 127 is lighted in its stead. jThe closing of thecircuit through relays 117 and 1416 causes the selectors 106 and 141 toadvance in the manner heretofore explained, until they reach their thirdposition, which is the position corresponding to the subscribers line12. In this position, as before, lamp 139 is lighted to indicate to theoperator which one of the subscribers lines is under observation.

As pointed out, the throwing of the listening key 86 results inenergizing relay 117.

The energization of relay 117 energizes relay 116. As soon as relay 116is energized a circuit is completed for relays 82 and 103 which extendsas before from batteries 173 and 174 through the windings of the relaysto the common point 172, and thence through closed contact 255,conductor 237, and closed contact 238 to ground. In case the centraloflice operator had depressed her ringing key 39 before the observingoperator had thrown her listening key 86, then the ringing currentflowing over the heavily marked circuit including conductors 78 and 79in parallel to the circuit provided by the subscribers line, would haveresulted in the energization of relay 104:, the current Hewing throughcondenser 271. As soon as re lay 104: had been energized in this way,the relays 82 and 103 would have their circuit completed from point 172through closed contact 255, alternate contact 257 and con ductor 258 toground. It will be noted that where calls originate upon the line underobservation, the relays 82 and 103 are operated as aresult of thesubscriber rentioving the receiver from its hook, while in the case ofcalls terminating upon the lines under observation, the same relays areoperated after the central oilice operator has plugged into the line,either at the time the observing operator throws her key 86, or thecentral oiiice operator applies ringing current to the called line. Itwill also be noted that in case the subscriber at substation 10, who isto be called, happens to remove his receiver from its hook to originatea call immediatelybefore the central oilice operator plugged into thejack of his line to call him, then relay 104; would not operate, andconsequently, the observing operators receiver 152 would not beconnected in circuit be cause of the failure of relay 82 to close itscontacts 17 5 and 177. In this case, however, the operation of relay 116following the throwing of the listening key 86, would permit the relays82 and 103 to operate.

When the central. otlice operator rings the called subscriber, relay 104is operated through condenser 271 so that in case of machine or keylessringing on the tip side ofthe line to ground, the low resistance shuntto ground through relay 102 would be cut off in order to prevent thetripping of the trip relay in a machine ringing trunk or cord circuit.The observer having previously thrown her listening key 86, can hear theringing through the listening circuit by reason of the repeating coilhaving the windings 81 and 83 which are bridged across the circuit,thelatter windings being separated by a condenser 272. During the silentringing interval, when ringing on the tip side of the line, the trippingbattery will operate relay 101 and open the circuit through relay 102,thereby preventing the the trunk, this relay will continue to operateduring the ringing interval and thus prevent the trunk tripping relayfrom operating until the called subscriber answers. The employment ofcondenser 271 in series with relay 104 reduces the chances of a centraloflice operator receiving a click when she plugs into a calledsubscribers line with her listening key thrown and bridges the trunkacross the line. The receiving of such a click would enable suchoperator to know that the line was under observation. In practice thecondensers 176, 271 and 273 are preferably of 2, 1.5, and .5 microfaradcapacity, respectively. When the called party responds to the ringing.of his bell by the removal of his receiver, relay 102 is operated bycurrent flowing over conductors 42, 58 and 78, closed contact 175 ofrelay 82, the winding of relay 101, closed contact 256, the winding ofrelay 102, normal contact 257, and conductor 258 to ground, as before.In this connection it may be pointed out that the right-hand winding ofrelay 101 is of relatively low resistance, while thatof the left-handwinding is of high resistance. For this purpose resistances of 20 ohmsand 2150 ohms respectively, may be employed. The opera- -.tion of relay102 connects battery to conductor 122 and thence through the Winding ofrelay 132 to ground at alternate contact 168 of relay 123, therebylighting the subscribers pilot lamp 125 as an indication to theobserving operator that the called party has responded by removing hisreceiverfrom its. hook.

At the conclusion of conversation the subscriber at substation 10 hangsup his receiver, the central ofiice operator takes down theconnection,andthese facts are indicated to. the observing operator by theextinguishing of lamps 127 and 125, and she thereupon restores herlistening key 86to normal. These operations produce the same results asheretofore described, and therefore need not be repeated.

As previously indicated, a line may be subject to observation both fororiginating and terminating calls but in some instances it may bedesirable to inspect the lines only for originating calls. In such casethe observing operator throws her key 135 and a portion of theoperations heretofore described; are. thereby prevented. Where thekey135 is thus thrown anda party at substation 10 initiates a call, thelamp 124ris lighted, in the manner heretofore explained, and-as soon asthe operator throws her listening key 86, the signal is transferred fromlamp'124to the subscribers pilot lamp 125. Following the throwing of thelistening key, relay 137 is operated by the closing of acircuit frombattery 275 through the winding-of relay 137, closed contact 270 ofrelay 123, and alternate contact 277 of key 135 to ground. hen thecentral olliee operator plugs into the calling line, the resultingoperations are the same as heretofore described except that the circuitoverlisten-ing conductor 84; through relays 105 and 130, extends fromconductor er through alternate contact 2 18 of key 135, normal contact278 of relay 137, and the win-ding of relay 130 to ground.

Now if subscribers line 12 be treated as a called line and the centraloflice operator plugs into the jack of that line, then with the key 135thrown, there will be no indications displayed before the observingoperator. Upon the insertion of the plug 24 into the jack 142 of theline 12, relay 06 will be operated as before and in consequence of itsoperation, relays 08, 71, 07, 98 and 09 will be operated as beforeexplained. As before, the operation of relay 70 causes the operation ofrelay 05. The operation of the latter establishes a circuit which may betraced from battery 245 through closed con tact 246, the winding ofrelay 105, conductor 2 17, repeating coil winding-83, listeningconductor 84, alternate contact 248- of key 135, normal contact 278 ofrelay 137, conductor 121, the winding of relay 100, normal key contact279, and normal. contact 205 of relay 118 to ground. The resultingenergization of relay 100 closes a circuit which may be traced fromground through closed contact-280 of relay 100, conductor 93, alternatecontact 281 of relay 71, normal contact 282 of relay 69, the winding ofrelay 69, and closed contact 283 of relay 08 to battery 153.

This latter relay upon being thus energized immediately locks up throughits alternate contact 282 and remains locked up until the connection istaken down and relay 68 thereby deenergized to open its locking circuitat contact 283. Since relay 69 is thus locked up, the battery suppliedto relays 70 and 71 is cut off and these relays together with relays 98,99, 95, 105 and 100 are restored to normal. The restoration of contact244 of relay 70 short-circuits the winding of relay 67 and causes it torestore its contacts 252,

253, and 254 by which the trunk conductors are connected through to thesubscribers line. In view of this cutting off of the trunk, it is clearthat signals from the subscribers line cannot be transmited to theobservingv station. When the connection is taken down as beforeindicated, relay 68 is deenergized and consequently relay 69 which hasbeen locked up is restored to normal.

Now if it be desired to observe only those calls which terminate uponthe subscribers lines, that is, those calls Where the subscribers linesare called-for lines, then key 135 is restored to normal and key 136 isthrown to its alternate position. With the keys in this position allcalls which originate upon the produce any indication before theobserving operator. Under these conditions, when the central oiiiceoperator plugs into the subscribers line,the operations are the same asheretofore described, this time the circuit for relay 130 extending fromlistening con.- ductor 84 through normal contact 248 of key 135. Whenthe observing opera-tor throws her listening key in response to thedisplay of lamp 126, the position relay 123 is operated as before and asa result of key 136 being in its alternate position, a circuit is alsocompleted for relay 137 which may be traced from battery 275 through thewinding of relay 137, closed contact 276 of relay 123, normal contact277 of key 135, closed contact 284 of key 136, and closed contact 251 ofrelay 130 to ground.

The operations following the removal of the partys receiver in responseto the call and the restoration of the receiver and the taking down ofthe connection, are the same as heretofore described.

If, under the same with the key 136 in its subscriber at substation 1Ooriginates a call by removing his receiver from its hook, then relay 68will be energized by reason of the closing of a circuit through itslower winding, as heretofore, and as a result of the energization ofrelay 68, relays 70, 71, 98 and 99 will be operated as before. Likewisethe closing of contact 163 of relay will close a circuit for relay 96over conductor 88 and cause said relay to operate just as heretoforedescribed. The operation of relay 96 completes a circuit which may betraced from battery 162 through closed contact 164 of relay 96 normalcontact 165 of relay 97, conductor 122, normal contact 166 of relay 123,alternate contact 167 of key 136, normal contact 285 of relay 137,conductor 121, the winding of relay 100, normal key alternate position,a

contact 279, and normal contact 205 of re lay'118 to ground. Theoperation of relay 100 operates relay 69, as before explained, andthelatter relay locks itself up through contact 283 of relay 68. As aresult of relay 69 bein locked up, battery is cut 06 of relays 76, 71,98 and 99 and they are restored to normal. The restoration of con tact244 of relay 70 short-circuits relay 67 and the observing circuitconductors 78, 79

subscribers lines will fail to condition, that is,

and 89 are disconnected from the line under observation so that anyoperations upon it cannot be transmitted through to the observingstation. As soonv as the connection is taken down, relay 68 isdeenergized and relay 69 unlocked so as t,o restore all the parts tonormal.

Attention is called to the fact that conductor 91, over which a holdingcircuit is closed for relays 70 and 71, is continued through normalclosed contact 229 of relay 71 to a corresponding contact upon the relay77. Thus when relay 71 is energized, contact 229 is opened, and nomaintaining circuit can be established for relays 76 and 77. This seriesarrangement is provided for the purpose of preventing a plurality ofcalls coming in on the one observing circuit. With this arrangement evenif two calls should happen to come in at the same time, relays 71 and 77would both partially operate through normal contact 157 of relay 98 thesame as before, but after these relays had completely operated, contacts156 and 286, by opening, would interrupt the initially energized circuitfor the relays 70 and 71, in the one case, and 76 and 77 in the other.In the case of relay 71, however, an alternative path would be providedthrough alternate contact 156 and conductor 91. This would not be thecase, however, with relay 77, for in that case the section of conductor91 running from alternate contact 286 would be opened at contact 229 ofrelay 71.

Attention is also called to the connection of conductor 92 to normalcontacts 281 and 287 of relays 71 and 77, respectively. This conductoris connected in this way so as to prevent the observing circuit beingimproperly brought into circuit. If, at the time the observing operatorcompletes the observation of a call over line 12 and restores herlistening key to normal, line 13 should be busy, then relays 76 and 77would operate to connect the observer to line 13 and in such case shewould not be observing a complete connection. However, with :theconductor 92 connected as shown, if a call is originated on line 13,while line 12 is connected'to the observing circuit, relay will beenergized over a circuit which may be traced from battery 288 throughclosed contact 289 of relay 74, the winding of relay 75, normal contact290 of relay 75, normal contact 287, conductor 92, and alternate contact157 of relay 98 to ground. When relay 7 5' is thus energized it will atonce lock itself up through its alternate contact and contact 289 ofrelay 74. Since this locked condition of relay 75 will continue untilthe connection with line 13 is taken down by the central ofliceoperator, it follows that it will be impossible for this line to beconnected by the energization of relay 67 to the observing 130 circuituntil such connection has been taken down. Thus the observing operatoris prevented from having her apparatus connected into the talkingcircuits of subscribers after the connections have been partiallycompleted. As previously pointed out, relay 67 has its winding normallyshort-circuited by contact 2% and consequently relay 67 cannot beoperated until relay 7 0 has been operated. The same is true of relays73 and 7 6 of the second group of relays. If the first group of relaysis. in service, then, as just pointed out, it will be impossible toestablish a maintaining circuit over conductor 91 for the energizationof relays 7 6 and 77. Therefore it will be impossible to remove theshort circuit, in this case provided by contact 290, from the winding ofrelay 7 3, and consequently it will be impossible to connect theobserving circuit conductors 7 8, 7 9 and 89, which are already in usewith line 12, to line 18, by closing contacts 291, 292 and 293 of relay7 3. Thus two subscribers lines cannot be connected to the one observingcircuit.

Relay 101, associated with the listening conductors 78 and 79, operatesduring the silent interval when ringing on the tip side of the line, aspreviously pointed out. When so operated, it opens the circuit throughrelay 102 and thus prevents the tripping relay in the machine ringingtrunk or cor circuits from operating. The resistance 29A between theleft-hand winding of this relay 101 and ground is added in order not toappreciably affect the margins of the tripping relay in the machineringing trunk or cord circuits when ringing on the tip side of the line.This particular resistance preferably has a value in the neighborhood of9800 ohms.

It will be apparent that in carrying out myinvention many changes indetails of parts and arrangements of circuits may be made withoutdeparting from the spirit and scope of my invention. I therefore aim tocover all such alterations and modifications bythe terms of the appendedclaims.

What is claimed is:

l. A pair of traveling switches, means to cause alternate movement ofsaid switches, and means to insure uniform movement of said switches bypreventing further actua tion of an advanced switch until the other ofsaid switches reaches a corresponding position.

2. A' pair of traveling switches, means to actuate .s'aid switches oneafter the other,

i and means to prevent subsequent operation of the farther advanced oneof said switches until both switches have been advanced an equal amount.

3. A- pair of traveling switches, means to actuate said switchesalternately, and means to prevent subsequent operation of the fartheradvanced one of said switches until the second of said switches arrivesin a corresponding position.

4;. A pair of traveling switches, driving circuit-s therefor, means toclose said driving circuits alternately, and means to hold open thedriving circuit of the farther advanced one of said switches until thesecond of said switches arrives in a corresponding position.

A telephone system including a plurality of sets of fixed contacts andcooperating wipers, means for advancing the first wiper, then stoppingit and advancing the second, then stopping the second and starting thefirst, and so on, first one and then the other, and means fordiscontinuing said advances.

6. A telephone system including a series of sets of cooperating fixedcontacts and wipers, means for advancing said wipers step by step,control means whereby said wipers successively take their first step,then in the same order their second, and so on, and means for startingand stopping the first wiper of the series.

7. A telephone system including a primary selector switch, means foradvancing said switch step by step, test means for discontinuing saidadvance, a follower switch, and control circuits and mechanism forintermittently delaying the advance of the primary switch and duringsuch delay periods advancing said follower switch.

8. A 'telephone system comprising telephone lines, link circuits for usein establishing connections with said lines, an observing trunk, meansfor severally uniting said lines to said trunk, signals correspond ingto said lines located at the observing end of said trunk, automatictraveling switches, means dependent upon a change in the normalcondition of a telephone line to cause said switches to display that oneof said signals which corresponds to said line, and means to insureuniform setting of said switches.

9. A telephone system comprising telephone lines, link circuits for usein est-ablishing connection with said lines, an observing trunk, meansdependent upon a changed condition of any one of said lines to connectsaid line to said trunk, signals corresponding to said lines located atthe observing end of said trunk, and automatic step-by-step switchmechanism for actuating that one of said signals which corresponds tothe said line having the said changed condition, and reciprocallycontrolled circuits for said step-by-step mechanisms to insure uniformsetting thereof.

10. A telephone system comprising telephone lines, link circuits for usein establishing connections with said lines, an 0bserving trunk, relaymechanism responsive to a changed condition of any of said lines toconnect said line to conductors of said trunk, a traveling switch havingpositions corresponding to said lines, means for causing said switch toadvance to a position corresponding to the said line having the saidchanged condition, a second traveling switch having positionscorresponding to the positions of said first switch, an operatingcircuit for each of said switches controlled in part by the other ofsaid switches, signals controlledby said second switch, and means fordisplaying said signals when said switches come to rest in advancedpositions.

11. A telephone system including two switches each having fixed andtraveling contacts, advancing and holding magnets and mechanism for eachof said switches, a control relay for said first switch advanc ingmagnet, a pair of control relays for said second switch advancingmagnet, a circuit for said first control relay extending throughnormally closed contacts of said pair of control relays, a fourthcontrol relay, a circuit for said fourth relay extending throughcontacts of said first switch, a circuit for one of the relays of saidpair extending through certain contacts of said second switch and anormal contact of said fourth relay, and a circuit for the other of.

the relays of said pair extending through other contacts of said secondswitch and an alternate contact of said fourth relay.

12. A telephone system including two electromagnetically controlledswitches, means for closing a circuit to advance the first of saidswitches one step, means responsive to said advance to interrupt saidcircuit and to close a circuit to advance the second of said switchesone step, means responsive to said latter advance to restore theadvancing circuit of said first switch and interrupt the advancingcircuit of said second switch, and test means for determining the extentof advance of said first switch.

13. A telephone system comprising telephone lines, link circuits forestablishing connection with said lines, an associated connectingcircuit extending to an observing station, an automatic finder switchfor connecting a telephone line to the connecting circuit, a signalingdevice correspond Copies of this patent may be obtained for five centseach, by addressing the Commissioner ing to each telephone line, anelectromagnetically controlled traveling switch adapted upon connectionof said line with the connecting circuit to cause the operation of thesignaling device corresponding to the connected line, and reciprocallycontrolled operating circuits for said traveling switch and said finderswitch to insure the setting of said traveling switch in a positioncorresponding to that assumed by said finder switch. V

14. A telephone system comprising telephone lines, link circuits forestablishing connection with said lines, an .associated connectingcircuit extending to an observing station, an automatic finder switchfor connecting a calling one of said lines to said connecting circuit, asignaling device at the observing station corresponding to eachtelephone line, a selectively controlled circuit for each signalingdevice, an electromagnetically controlled traveling switch 0perativeupon connection of said calling line to said connecting circuit tocomplete the circuit of the signaling device correspond ing to saidcalling line, and means to prevent the setting of said traveling switchin a position ahead of that assumed by said finder switch.

15. A telephone system comprising telephone lines, link circuits for usein establishing connections with said lines, an associated observingcircuit extending to an observing station, line and link circuit signalsat said station for indicating the relative conditions of said lines andlink circuits, means responsive to changes in the conditions of saidlines and link circuits to display said signals, other signalscorresponding to said lines, automatic traveling switches for displayingsaid other signals in accordance with the said changes in the conditionsof said lines, means for starting said switches, means under theobserving operators control for preventing certain conditions fromaffecting said signals, and circuits for said switches each being controlled in contacts of the other.

In witness whereof, I hereunto subscribe my name this 29th day ofSeptember A. D.

ALBEN E. LUNDELL.

of Patents,

Washington, D. G.

